Do not wash anything that is not marked 'dishwasher proof' or 'dishwasher safe' in a dishwasher. Other items that should not be washed in a dishwasher include:
Acrylic: Small cracks may occur.
Adhesive-Joined Pieces: Adhesives that join materials such as plastic, wood, bone, steel, copper, tin, etc. may loosen.
Bone-Handled Utensils: Handles may separate.
Iron: Iron will rust. Hand wash and dry immediately.
Non-Dishware Items: Your dishwasher is intended for use in cleaning standard household dishware and kitchenware only.
Pewter, Brass, Bronze: These metals will tarnish. Hand wash and dry immediately.
Tin: Tin will rust. Hand wash and dry immediately
Wood: Wooden bowls, utensils and wooden-handled utensils can crack, warp and lose their finish.